More thread-safety changes

[Zoxc]

r? @michaelwoerister

[bors]

☔ The latest upstream changes (presumably #49558) made this pull request unmergeable. Please resolve the merge conflicts.

[michaelwoerister]

Could the arena case not be handled by wrapping arenas in a mutex instead of hard-coding the mutex into the arena types? This way one could decide on a case-by-case basis if an arena needs to be synchronized or not.

[Zoxc]

No, arenas and mutexes do not compose. We could have a thread-safe and thread-unsafe variants of the arenas however. That would probably reduce the amount of changed lines too.

[michaelwoerister]

Can you elaborate on that? Do you mean that one can't use a thread-unsafe arena where a thread-safe arena is expect?

[Zoxc]

If you use a Mutex<Arena> the lifetimes of the allocated objects will be restricted to the mutex guard.

[bors]

☔ The latest upstream changes (presumably #49396) made this pull request unmergeable. Please resolve the merge conflicts.

[rust-highfive]

Your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

[00:00:46] configure: rust.quiet-tests := True
---
[00:05:31] error[E0596]: cannot borrow immutable borrowed content as mutable
[00:05:31] --> libarena/lib.rs:447:9
[00:05:31] |
[00:05:31] 447 | self.lock.lock().clear();
[00:05:31] | ^^^^^^^^^^^^^^^^ cannot borrow as mutable
[00:05:31]
[00:05:31] error: aborting due to previous error
[00:05:31]
[00:05:31] For more information about this error, try `rustc --explain E0596`.
[00:05:31] error: Could not compile `arena`.
[00:05:31]
[00:05:31] Caused by:
[00:05:31] process didn't exit successfully: `/checkout/obj/build/bootstrap/debug/rustc --crate-name arena libarena/lib.rs --color always --error-format json --crate-type dylib --emit=dep-info,link -C prefer-dynamic -C opt-level=2 -C metadata=dd80e21b25e89693 -C extra-filename=-dd80e21b25e89693 --out-dir /checkout/obj/build/x86_64-unknown-linux-gnu/stage0-rustc/x86_64-unknown-linux-gnu/release/deps --target x86_64-unknown-linux-gnu -L dependency=/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-rustc/x86_64-unknown-linux-gnu/release/deps -L dependency=/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-rustc/release/deps --extern rustc_data_structures=/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-rustc/x86_64-unknown-linux-gnu/release/deps/librustc_data_structures-93cb1ddd29ab61a4.so` (exit code: 101)

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[Zoxc]

I added thread-safe variant of the arenas instead of modifying the existing types.

[michaelwoerister]

I added thread-safe variant of the arenas instead of modifying the existing types.

Thanks, I think that's an improvement.

[michaelwoerister]

Could the local arenas in theory be non-synchronized?

[Zoxc]

All the arenas could be thread-local if we find a way to deal with lifting of types.

[michaelwoerister]

Looks good to me. Thanks, @Zoxc!

@bors r+

[bors]

📌 Commit fe63637 has been approved by michaelwoerister

[bors]

⌛ Testing commit fe63637 with merge 6b12d36...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: michaelwoerister
Pushing 6b12d36 to master...